Radiotube



Patented Feb. 21, 1933 UNITED STATES PATENT OFFICE I ALLEN B. DU MONT, OF IBIJOOMIFIELD, NEW JERSEY, ASSIGNOR TO DE FOREST RADIO COIPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF DELAWARE RADIOTUBE Application filed November 26, 1928. Serial No. 321,848.

This invention relates to improvements in radio tubes.

One of the objects of this invention is the provision of a new form of electron discharge device in which the usual plate thereof is made in the form of a coil of wire and which, in conjunction with the grid coil, provide the inductively related coils by means of which the plate and grid circuits are associated to provide a feed back circuit.

A further object of this invention is the provision of an electron discharge device which is particularly adapted for the generation of exceedingly short waves.

A further object of this invention is the provision of a short wave or high frequency generator and connections therefor which are exceedingly simple and adapted for extreme compactness.

These and other objects as will appear from the following disclosure are secured by means of this invention.

Referring to the drawing Figure 1 is a diagrammatic illustration of a standard form of transmitting circuit employing the feed back principle.

Fig. 2 is a. diagrammatic illustration of the improved vacuum device of this invention and the circuits therefor whereby extremely high frequencies may be generated.

Although this invention is disclosed as applied to a transmitting system it is to be distinctly understood that the principles thereof are applicable to receiving systems and it is intended that the claims cover both.

One of the difiiculties encountered in producing electron discharge devices which will oscillate at extremely high frequencies is the capacity effect of long leads connecting the electrodes of the device with the other circuit instrumentalities and, in addition, the effect caused by the resistance of these leads. In

roducing a. vacuum device which will oscilate at a fraction of a wave length the capacity of these leads and of the electrodes,

although exceedingly small becomes of ma'or importance and, in fact, the determimng factor which limits the frequency at which the device can be made to oscillate. This invention contemplates the idea of making the usual plate and grid electrodes form the primary and secondary of the transformer by means of which the output energy in the plate circuit is fed back to the input or grid circuit. By employing these two electrodes for this purpose it is possible to eliminate the long leads and, in fact, any leads at all. This thought is true where the device is made for the particular purpose of generating currents of a single high frequency where it is not necessary to provide any capacity adjusting means to tune the two circuits. Another highly important advantage of this arrangement is that the tube becomes much more sensitive because of the combined electrostatic and electro-magnetic control of the electrons by reason of the presence of the currents in the two coil electrodes within the vessel.

A standard transmitting circuit is shown in Fig. 1 for purposes of comparison. The oscillating audion is shown with the exhausting vessel 1 taking the plate anode 2, grid 3 and filament or cathode at supplied from the current source 5. The anode is connectedby wire 6 to one terminal of the current source 7, the other terminal of which is connected by wire 8 to the inductance 9. The other terminal of the inductance 9 is connected to one terminal of the grid inductance 11 which has its other terminal connected to the grid 3 by wire 12. A lead 10 connects the cathode circuit to a point between the inductances 9 and 11. The antenna circuit is shown comprising the antenna 13 connected to one terminal of the-inductance 14, the other terminal of which is grounded. The inductances 9 and 11 are closely associated with the inductance 14. A short circuiting wire including a switch 16 is provided by means of which a number of turns of the inductance 14 may be short-circuited upon the closing of the switch 16 to detune the antenna circuit. An audion circuit of this type provides a source of alternating current which is sent out over the antenna as a continuous wave, the continuity of which may be periodically interrupted b the closing of switch 16 for the purpose 0 transmitting intelligence.

When employing an arrangement of this nature for the production of exceedingly high frequencies it is found that the upper limit of frequency is determined by the capacity inductance and resistance characteristics of the leads necessary to connect the audion device to the external circuit instrumentalities. To overcome this difliculty it is proposed to make the grid and plate electrodes perform the function of the inductances 9 and 11 (Fig. 1).

Referring to Fig. 2 the electron discharge device is shown comprising an exhausted vessel 17 having the reentrant stem tube 18. The plate electrode which is usually in the form of a sheet of metal is shown in this case comprising a coil of wire 21 wound upon the insulating supports 19 and 20. The grid electrode is shown as the usual wire coil but, in this case, also supported upon insulating supports 23 and 24. The insulating supports 20, 24, 23 and 19 are supported upon wires secured to the stem tube 18. These insulating supports have been indicated as secured to the supporting wires by means of the black marks indicating a joint as shown at 20 and 19". The specific features of construction are of no reat concern here since they may take a numier of forms. For instance, the insulating supports to extend directly to the stem tube and be secured therein and then leads taken off directly from the plate and grid electrodes. The grid electrode 22 is connected by the wire 41 to the wire support 41 and the plate electrode 21 is connected by the wire 25 to the wire support 25. The cathode is shown at 40 having the leads 31 which connect it to the current source 32. Supporting wire 41 is connected to the wire 34, and supporting wire 25 is connected to tlvewire 26. Awire 33 extends from the positive side of the current source 32 and an adjustable condenser is placed across the-wires 34 and 33. Wire 26 is connected to the positive side of the current source 27, the negative side of which is connected to one terminal of the inductance 28. The other terminal of the inductance 28 is connected by a wire 30 to the positive side of the current source 32. A variable condenser 29 is connected across the wires 26 and 30. The antenna system is shown com-- vide a feed back of energy the plate electrode 21 and the grid electrode 22 are employed as these inductances and are associated with each other within the evacuated vessel. The inductance 28 is provided as a means through which the oscillating energy may be delivered for any use. The condenser 29 is provided to tune the plate circuit of the device to vary the frequency of the current generated while condenser 35 controls the feed back of energy, but it is at once apparent that when the device is made to generate one frequency only these condensers canbe eliminated by designing the device to have the proper capacity to generate the desired frequency. Likewise, other means of removing the energy generated may be employed in place of the inductance 28, which could consist of a coil surrounding the tube. This device readily lends itself to extreme compactness and the few leads that are needed may readily be reduced to a minimum of length. The vacuum device becomes completely within itself, with the exception of the energy source, a generator of high frequency currents. It is, of course, apparent that the device is not necessarily limited to extremely high frequencies since lower frequencies could be generated thereby. An additional advantage of the device is that the currents flowing in the grid and plate circuits will flow directly through the grid and plate electrodes within the vessel and being closely associated with the cathode will aid in the control of the electrons through electro-static and electro-magnetic effects.

I .am well aware that many changes in the detail of construction, relative arrangement of parts, and circuit connections will readily occur to those skilled in the art and I do not, therefore, desire to be strictly limited to the illustrations given, but rather to the principle and scope of this invention.

What I seek to secure by United States Letters Patent is 1. An electron discharge device compris- 1ng an evacuated vessel having a press, a cathode supported within said vessel, and two additional electrodes comprising wire coils mounted within said vessel to act as the plate and grid electrodes of the device, and also as the plate and grid inductances by means of which the input and output circuits of the device are coupled, a pair of insulating supports around which said coils are wound, metal supports sealed into said press and supporting said insulating supports, and a lead-in wire for only one end of each of the coil electrodes whereby said electrodes act as openend inductances.

2. An electron discharge device comprising the combination of an evacuated envelope having a press, a cathode within said envelope, a pair of electrodes surrounding said cathode and each comprising a coiled wire having the turns wound around a pair of insulating supports, metallic wires sealed into said press and supporting said insulating supports.

In testimony whereof I have hereunto set my hand on this 21st day of November, A. D.

ALLEN B. DU MONT. 

